1. Field of the Invention
The present invention is directed to a fastener having a unique configuration along its shank and useful primarily for fastening a work piece to a metal substrate.
2. Description of the Related Art
Fasteners of various configurations are known for fastening relatively thick work pieces, such as drywall, to various substrates, such as metal framing members. Commonly, such fasteners have elongate shanks defining axes and include smooth and flat heads to be axially driven by power tools, such as pneumatically-powered or combustion-powered tools.
Fasteners for fastening a work piece to a metal substrate are shown in U.S. Pat. No. 5,489,179 to Gabriel et al., U.S. Pat. No. 5,741,104 to Lat et al., and U.S. Pat. Nos. 6,171,042 and 6,203,442 to Olvera et al., all assigned to the assignee of this application, and published U.S. patent application Ser. No. 2002/0071741 to Oswald. These references show fasteners with knurling on their shanks that typically includes helical grooves for channeling dust and rotating the fastener as it is driven and annular grooves for engaging with the substrate for high pullout strength.
However, because of this high pullout strength, it is difficult to remove the work piece for electrical work or plumbing without damaging or destroying the work piece, particularly if the work piece is gypsum drywall, because the fastener has to be pried out of the work piece with a hammer or other prying tool with enough force to overcome the pullout strength. This damage and destruction can be very undesirable, particularly if the work piece is merely being removed temporarily, in which case an entirely new work piece would have to be installed, requiring considerable added material costs.
One might think that the helical grooves would allow the fastener to be rotated to disengage it from the metal substrate, but it has been found that the fastener merely spins in place and does not become disengaged because the annular grooves remain engaged with the metal substrate and because the helical grooves are not threads. The pitch of the helical grooves is designed for channeling dust and for increasing pullout strength, not for threaded disengagement.
What is needed is a fastener for fastening a work piece to a substrate that can be removed without damaging the work piece.